1. Field of the Invention
The present invention relates to a sheet processing device, an image forming system, and a sheet processing method. Specifically, the present invention relates to a method for processing a sheet conveyed in a folded state.
2. Description of the Related Art
In recent years, electronification of information tends to be pushed forward, and image processing devices are absolutely necessary such as a printer or a facsimile used for outputting electronified information and a scanner used for electronifying documents. In many cases, such an image processing device may be configured as a multifunction peripheral having an image capturing function, an image forming function, a communication function, and the like to be utilized as a printer, a facsimile, a scanner, and a copying machine.
Among such multifunction peripherals, known is a multifunction peripheral on which a folding processing device is mounted, the folding processing device performing folding processing on a sheet on which an image is formed after the image is formed on the fed sheet to draw the image. When such a folding processing device performs folding processing on the sheet, a fold is weak and incomplete, causing a folding height to be high as it is. Accordingly, among such multifunction peripherals, known is a multifunction peripheral on which a fold enhancing device is mounted in addition to the folding processing device, the fold enhancing device performing fold enhancing processing for enhancing the fold by pressing the fold formed through the folding processing to enhance the fold and reduce the folding height (for example, refer to Japanese Patent Application Laid-open No. 2013-060246).
Examples of a method for performing fold enhancing processing by such a fold enhancing device include a method for pressing a fold formed on a sheet while conveying the sheet with a fold enhancing roller having a length corresponding to a sheet width that is laterally bridged in a direction (main-scanning direction) parallel to the fold formed through the folding processing. Examples of another method for performing fold enhancing processing by the above-described fold enhancing device include a method for sequentially pressing a fold formed on a sheet in a main-scanning direction by temporarily stopping conveyance of the sheet at a position where fold enhancing processing is performed, and moving the fold enhancing roller rotating around a rotation axis along a direction (sub-scanning direction) perpendicular to the fold formed through the folding processing, in the main-scanning direction on the stopped sheet.
However, in the fold enhancing processing method as described above, a folding wrinkle or a pressed mark may be formed on the sheet after fold enhancing processing. Such a problem may arise in a sheet-like object which is not limited to a sheet for forming and outputting an image.
In view of such a situation, there is a need to improve quality of a sheet after enhancing a fold thereof in a sheet processing device for enhancing the fold of the sheet conveyed in a folded state.